1.6hdi cooling fan

[xsara92]

Hi folks
Does anyone have a link to info on conditions that cause the cooling fan to operate on the 1.6hdi 16v?
I don't know if mine has ever been on, but I'm not sure, that might be correct for a temperate climate and not exceeding 80mph...

[PaulC5]

See if it works with the air con on as one check. For a hot engine you need to look at live data and see what temperature the engine is at. Often about 96°C will be the first switch on of the fan and on 2 speed fans a few degrees higher for the faster speed to start. When driving along the engine might not get hot enough for the fan to start but if stationary for a long time it might.

[Essay]

I drove my 2.0 HDI C5 for a year before I realised the fan was cactus. Much better now with one purchased for £75 at the wreckers. Switch on A/C, should be on

[xsara92]

Thanks both,
So I checked with the car stationary engine running, A/C on - fan still.
Interestingly my A/C was working, but has next to no effect now (sometimes feels cooler with just minimum temp but A/C off).
Also a revelation to learn the fan should be needed most when still. I thought engine work rate was the dominant factor
Can a dead cooling fan harm the A/C unit or is tue ECU smart enough to reduce the load on the system (yet I have no MIL, but do need a code reader)
I hope not, can't afford to renew the whole thing
@Essay, do you mean you had engine performance issues before renewing the fan or just talking about A/C effectiveness?

[PaulC5]

For the air con to work it needs the engine fan (and cabin fan) to run, possibly on and off to control the pressure of the refrigerant. If the air is not cooling much then it may be the refrigerant needs regassing, normal after a few years, our C5 had it done at 7 years and also at 14 years when the condenser had a leak.

When the car is moving air flows over the radiator naturally and the flow rate increases with road speed so cooling rate increases as you speed up. It is when stopped or moving slowly the air flow reduces so the cooling rate is a lot less and then needs the fan. If going slowly up a long hill in a low gear the engine would be working hard so then the fan might come on.

Problems with the air con or fan are unlikely to put the engine management light on so any faults would not be seen on a low cost code reader. However, if you get one with live data it will give the coolant temperature so will help.

[xsara92]

Great explanation Paul.
This car is 20 years old. A/C actually just marginally works I think, yesterday eve I noticed it when it was really warm till late.
Think I'll do a test with a steep hill next to be sure but given it doesn't work with A/C stationary I probably need to get the fan replaced, hope they still produce one that fits the Xsara Picasso

[thorter]

Just to add to Paul’s helpful information, the coefficient of performance (COP) of any heat pump, refrigerator, aircon etc varies depending on the temperature difference between its hot and cold sides. COP boils down to amount of heat output or removal divided by amount of heat or energy input. Clearly some devices and types of devices will be more efficient than others, but typically the COP might be 10 for next to no temperature difference (when you wouldn’t bother anyway), to perhaps COP of 2 for 40°C difference (when you really need the heating or cooling). Beware of COP specified for 10°C temperature difference!

For interest, fighter aircraft need to cope with a temperature difference of more than 100°C, and the cooling system can only be configured as a heat pump with a COP in these circumstances as low as 1.1. Thus 10 units of input energy are needed for one unit of cooling, thus using up kilowatts of engine power.